The prior art teaches a method of constructing poured concrete walls in which modular wall preforms, each comprising a pair of high-density foam panels which are maintained in a parallel-spaced relationship by a series of bridging "webs" extending between and through and molded into the panels, are interlockingly stacked together to define a concrete form for the poured concrete wall. With reinforcing steel bars optionally suspended within the assembled wall form, preferably through use of hooks or other retainers provided on each bridging web, the concrete is thereafter poured between the panels to complete the wall.
Unlike other known methods of constructing poured concrete walls in which the form's panels are removed from the poured concrete wall prior to the complete curing thereof, in the method employing these modular foam-panel preforms, the preforms become a permanent part of the resulting composite wall structure, with the interlocking foam panels providing a highly-effective layer of insulation on both sides of the finished wall. Further, where the webbing terminates on the outside of each panel to define integral furring strips, finishing materials may be conveniently applied directly to the interior and exterior of the wall.
While this method has proved highly successful in constructing poured concrete basement walls, with first-floor joists supported by the wall's top surface in a conventional manner, there remains a need to provide a simple yet effective apparatus and method by which joists may be supported by the wall at a height beneath its top surface.
More specifically, in a first known method of supporting joists at a height beneath the wall's top surface, after stacking several courses of modular preforms, and before pouring the concrete, the joists are laid out across the stacked preforms such that the end of each joist projects beyond the interior panel to a sufficient depth within the wall form. Special notched-panel preforms are thereafter assembled between and on top of the joists to define the portions of the wall therebetween, and the concrete is thereafter poured to a height above the top of each joist's inwardly-projecting end.
Unfortunately, this first method for supporting joists requires the concurrent and precisely-coordinated efforts of tradesmen skilled in both concrete and carpentry, with an attendant increase in labor costs. Additional bracing for the joists and modular preforms is often required. A failure to properly position the projecting joist end relative to the preform can substantially effect either the quality of the support provided by the wall or the integrity of the wall, or both. Building codes often prohibit direct contact between concrete and wood and, further, provide that joists imbedded within concrete be "fire cut" with a vertical chamfer such that the joist's upper edge does not catch the wall, thereby reducing the load-bearing capacity of such embedded joists. And, of course, the vertical repositioning of any given joist is virtually impossible. Perhaps most significantly, this first method often results in the creation of air pockets or "voids" in the poured concrete wall directly beneath each projecting joist end. Such voids can significantly contribute to premature failure of the juncture of wall and joist.
In accordance with a second known method for supporting joists at a height beneath the top surface of a poured concrete wall, U-shaped metal brackets are inserted through a series of spaced, complementary U-Shaped holes cut in a given course of foam preforms such that one end of the bracket extends well into the hollow space between the two foam panels. The other end of the bracket continues to project from the surface of the interior panel to provide a U-shaped hanger into which a given joist may be placed. The bracket includes nailing apertures to facilitate nailing the joist to the bracket.
While the second method is readily practiced by concrete tradesmen alone, the bight portion of the U-shaped bracket renders the second method particularly susceptible to void formation beneath each bracket. Moreover, since the holes in the interior panel are sized so as to tightly receive the bracket, the concrete does not flow into the holes. As a result, in the finished wall, each joist is undesirably supported by the bracket in an extended cantilevered fashion, with the end of the joist spaced from the poured concrete a distance equal to the thickness of the interior panel. Additional failure modes are thus created in a building constructed in accordance with this second method.
In accordance with a third known method for supporting joists at a height beneath the top surface of a poured concrete wall, rectangular, rearwardly-tapering holes are cut in a given course of the stacked foam preforms. A wood ledger, preferably of the same vertical dimension as the floor joists, is fastened with screws to the interior panel such that the ledger covers each hole. The ledger is thereafter drilled and L-shaped anchor bolts inserted therethrough so as to extend well into the hollow space between the two foam panels. After the concrete is poured, and with the anchor bolts tightened only after the concrete has completely cured, joists are thereafter nailed to the ledger using conventional metal joist hangers.
While its rearwardly-tapering holes facilitate the flow of poured concrete around each anchor bolt and, hence, reduce the occurrence of deleterious voids in the finished wall, the third method for supporting joists is highly labor-intensive and time-consuming, requiring the discrete, serial steps of: forming tapered holes; sizing and positioning the ledger; attaching the ledger to the interior panel; drilling holes in the ledger for the anchor bolts; inserting the anchor bolts, exercising care to ensure that each anchor bolts extends a sufficient depth into the form; pouring the concrete, preferably while mechanically vibrating the stacked preforms to facilitate flow of the concrete into the tapered holes and about the anchor bolts; waiting for the concrete to cure; tightening the anchor bolts, thereby drawing the ledger against the concrete projections defined by the tapered holes; nailing conventional joist hangers onto the ledger; and inserting and nailing the joists in the joist hangers.